Strongly coupled exciton-plasmon nanohybrids reveal extraordinary resistance to harsh environmental stressors: temperature, pH and irradiation

The enhancement of light-matter interaction through strong coupling is a convenient strategy for the development of photonic devices. Usually, the systems under strong coupling regime suffer from poor structural stability. The present study demonstrates outstanding resistance of these structures to harsh stressors. 

Hybridized plexcitonic states have unique properties that have been widely studied in many research fields targeted at both fundamental science and innovative applications. However, to make these applications come true one needs to ensure the stabilization and preservation of electronic transitions in hybrid nanostructures, under the influence of external stressors in regimes that have not yet been comprehensively investigated.

Among other strongly coupled structures, localized plasmon/exciton complexes attract special attention because of the possibility to enormously minimize the mode volume in these systems. However, the use of plasmonic nanoparticles as nanoresonators and J-aggregates as quantum emitters imposes specific requirements on the hybrid system, one of which is the stability of exciton–plasmon hybridization under environmental stress.

The present work shows that nanohybrid systems, composed of plasmonic nanoparticles and J-aggregates of organic molecules, display outstanding resistance to harsh environmental stressors such as temperature, pH and strong light irradiation as well as demonstrate long-term stability and processability of the nanostructures both in weak and strong coupling regimes.

Specifically, the spectral features associated both with weak and strong coupling effects in hybrids based on Au nanoparticles and J-aggregates of cyanine dye were found to be stable over several weeks, upon temperature changes between 10 and 70 °C and pH in the range from 4 to 10. They are also able to withstand high-power irradiation on an unprecedented timescale. In addition, a morphologically induced alteration of the plasmon–exciton coupling strength has been revealed, which is the consequence of the difference in quality factors and local field enhancement generated by nanoparticles of two different shapes. Researches envisage that these findings can be exploited for the development of advanced highly stable devices for optoelectronic, bioimaging and sensing applications. These findings also contribute to a deeper understanding of the physicochemical properties of plexcitonic nanoparticles.

Figure: Photostability of nanohybrids irradiated with varying power density and size distribution histograms of two hybrid samples (TEM images in inset) before and after irradiation.